— 2 4 — 



add this to the milk in the boiling flask ; do the same with acetic 

 acid, and mix the whole well together by shaking. Place the 

 flask in the water bath, in which the water must be boiling quiet- 

 ly during the whole operation. While this sample is being heated 

 another may be made ready by the addition of the acids, and then 

 set in the bath. The heating of each flask should be limited to 

 five or six minutes, and during this time the contents of the flask 

 should be shaken once or twice ; it is quite important to keep the 

 acids and the milk all the time well mixed together. When the 

 boiling is finished, set the flask in cold water ; it will be well to 

 complete the heating of all the samples in hand before proceeding 

 to the next step, as none of them should be boiled more than the 

 time stated above. 



When the flask is cold add 4 c.c. of ether, measured out in the 

 other measuring tube, mix well by shaking, and set the flask 

 again in the boiling water for ten or fifteen minutes, or till no 

 smell of ether is perceived at the mouth ; this treatment may be 

 given to as many flasks at once^as there are places in the water 

 bath. As the result of this operation a layer of clear fat appears 

 at the surface of the liquid. 



Holding the fat-measure by the upper end of the side tube, sink 

 it in boiling water till a little runs in at the mouth of the 

 graduated tube, and hold it there a minute or two ; then 

 pour out the water that has run in, and pour at once the contents 

 of one of the boiling flasks, taken directly from the water 

 bath, into the side tube, rinse the boiling flask with a little boil- 

 ing water, and pour this in at the side tube, and repeat this 

 rinsing two or three times, or till all the fat is in the fat meas- 

 ure. Then, with boiling water in a little pitcher, with a very 

 small spout, pour more water in at the side tube, thus raising 

 the fat into the graduated tube, and as the level of the liquid 

 approaches the lower end of the graduated tube, add the water 

 very slowly ; the last portion of the water should be added 

 very carefully so as to bring the lower levels of the column of 

 fat just a little above the lower limits of the graduation. If the 

 column of fat is not perfectly unbroken, a defect that may arise 

 from the entanglement of water with it, get it together by run- 

 ning a very small wisp from a broom up and down through it. 



Then at once read off the upper and lower levels of the column 

 of fat, reading from the lowermost point of the curved surface of 



